a The atoms marked with asterisks are the reactive atoms with the extrema given in the table.

3.1.2 Geometries and Interactions

The schematic diagram for structure of the binary complex with pnicogen bonding is displayed in Figure 2, and the optimized geometries of these R-Ph-CN…PO2F complexes are shown in Figure S2, in which PO2F is approximately perpendicular to the R-Ph-CN molecular frame, and R denotes one of the several substituents chosen in this study. Since our interest is the study of the papa-substitution effect and cooperativity effect on the pnicogen bonding, some other structures which may exist for R-Ph-CN…PO2F complex are not considered here anymore. The structures can be understood with the following MEP analysis of the molecules.